Shear and seal system for subsea applications

ABSTRACT

A system and methodology facilitates utilization of a valve and a cutter both of which may be used in a subsea test tree. The valve comprises a ball element pivotably mounted in a housing and having an exterior surface and a passageway sized to receive a conveyance therethrough. The cutter also is located in the housing but at a position spaced from the ball element. The cutter is oriented for selective severing of the conveyance. Additionally, a seal system is positioned to act against a surface of the ball element.

BACKGROUND

Hydrocarbon fluids such as oil and natural gas may be obtained from subsea wells. Subsea test trees enable well testing and well cleanup operations to be conducted on subsea wells from an offshore floating rig. In the event the well is to be shut down, the subsea test tree includes valves for shutting in the well and for preventing discharge of the landing string contents into an associated riser. Additionally, various clean up or well testing operations may involve running a conveyance mechanism, such as a wireline or coiled tubing, through the subsea test tree. The subsea test tree also may comprise a mechanism for cutting and removing these conveyance mechanisms and for providing a leak tight barrier in the bore after cutting and removing the conveyance mechanism.

SUMMARY

In general, the present disclosure provides a system and method of utilizing a valve and a cutter both of which may be used in a subsea test tree. The valve comprises a ball element pivotably mounted in a housing and having an exterior surface and a passageway sized to receive a conveyance therethrough. In many applications, a ball element actuation mechanism may provide an optimized force output between a lower limit that is sufficient to close the valve and an upper limit that is low enough to accommodate stripping of the conveyance through the valve without pinching. Additionally, a seal system is positioned to act against a surface of the ball element. The cutter also is located in the housing but at a position close to but spaced from the ball element. The cutter is oriented for selective severing of the conveyance.

However, many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein, and:

FIG. 1 is a schematic illustration of a subsea well system having a subsea test tree with a cutting and sealing system comprising a cutter and a valve separate from the cutter for sealing off a flow-through passageway through the subsea test tree, according to an embodiment of the disclosure;

FIG. 2 is a cross-sectional view of an example of a cutting and sealing system having a valve separate from a cutter in a common housing, according to an embodiment of the disclosure;

FIG. 3 is a cross-sectional view similar to that illustrated in FIG. 2 but showing the cutter in an actuated or cutting position, according to an embodiment of the disclosure;

FIG. 4 is a cross-sectional view similar to that illustrated in FIG. 3 but showing the valve actuated to a closed and sealed position, according to an embodiment of the disclosure;

FIG. 5 is a partial cutaway view of the valve in the form of a ball valve having a rotatable ball element, according to an embodiment of the disclosure; and

FIG. 6 is a cross-sectional view of another example of the cutting and sealing system, according to another embodiment of the disclosure.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

The present disclosure generally involves a system and methodology utilizing a cutting and sealing system having a valve and a cutter. The cutting and sealing system may be used in a subsea test tree. In an embodiment described in greater detail below, the valve comprises a ball valve having a ball element pivotably mounted in a housing which also serves as a housing containing the cutter at a separate location. In many applications, a ball element actuation mechanism applies a biasing force to the ball element such that the force output is optimized between a lower limit sufficient to close a valve and an upper limit that is low enough to accommodate stripping of the conveyance through the valve without pinching. Additionally, a seal system may be positioned to act against a surface of the ball element. Other types of valve elements also may be employed in some applications. The ball or ball element has an exterior surface and a ball passage sized to receive a conveyance therethrough. The cutter is oriented for selective severing of the conveyance at a position separate from but very close to the location at which a seal system seals against an exterior surface of the ball element. This arrangement enables cutting of the conveyance independently of the sealing function while also allowing a rapid sealing off of the flow-through passageway upon severing of the conveyance.

The valve element may be actuated between an open position and a closed position blocking the passageway. If the valve element comprises a ball, the ball is pivoted between an open position, which allows flow of fluid through the internal ball passage and along the overall flow-through passageway, and a closed position, which blocks flow of fluid along the overall flow-through passageway. In some applications, the ball element may comprise a relief area which is positioned to allow the ball to begin closing before the conveyance is pulled clear of the ball passage upon severing of the conveyance. The relief area facilitates rapid closing of the overall flow-through passage once the conveyance is cut.

Depending on the application, the cutter also may comprise a variety of components and configurations. For example, the cutter may comprise a plurality of cutting elements, e.g. blades, mounted on radial actuators. The radial actuators may be in the form of pistons, e.g. hydraulic pistons, or other actuators that may include other types of hydraulic actuators, electromechanical actuators, or other suitable actuators having sufficient power to cut through the conveyance. In a specific example, the cutting elements comprise blades which are mounted to hydraulically actuated pistons powered by a suitable hydraulic actuating fluid which may be delivered through a variety of control lines, ports, and/or other passageways. The hydraulically actuated pistons are mounted radially in a surrounding housing to enable controlled movement of the cutting blades in a radially inward direction to selectively sever the conveyance. By way of example, the system may utilize a pair of hydraulically actuated pistons or other types of actuators, although the system may be designed to accommodate additional cutting blades/actuators or an individual cutting blade and actuator.

In a subsea test tree application, a subsea test tree is employed to enable well testing and well cleanup operations to be conducted from, for example, an offshore floating rig. The cutting and sealing system is combined into the subsea test tree installation and may be employed to reliably and repeatedly cut conveyances, e.g. coiled tubing, wireline, or other conveyances, and to provide a gas tight seal after severing of the conveyance. In embodiments described herein, the cutting and sealing system utilizes a cutter ram and a strip through ball valve although various other components and component configurations may be used in forming the cutting and sealing system.

The cutting and sealing system provides a fast acting and reliable system to shut-in the well with two barriers and to prevent discharge of the landing string contents into the riser. The cutting and sealing system also provides a fast acting and reliable system for disconnecting the landing string from the test string in well testing and well cleanup operations. In operation, the cutting and sealing system of the subsea test tree initially cuts and removes the conveyance medium (e.g. coiled tubing, slickline, or wireline) that may be present, and then provides a gas tight barrier/seal in the wellbore before disconnecting. This dual functionality is achieved by the cutting and sealing system installed as part of the subsea test tree.

Referring generally to FIG. 1, an embodiment of a system, e.g. a subsea well system, is illustrated as comprising a cutting and sealing system designed to shear a conveyance and to seal off a passageway. In this example, the cutting and sealing system is employed in a subsea test tree, but the cutting and sealing system also may be employed in other types of subsea or surface well equipment. The valve may be designed to accommodate passage of many types of conveyances, including coil tubing conveyances, wireline conveyances, slickline conveyances, and other suitable conveyances, as such conveyances are moved along the overall flow-through passageway within the subsea well system. It should further be noted the cutting and sealing system may be used in combination with other types of equipment in both well and non-well related applications.

In the example of FIG. 1, a subsea well system 20 is illustrated as comprising a surface structure 22, e.g. a floating rig, positioned at the sea surface 24. The surface structure 22 may be coupled with a subsea test tree 26, located at a seafloor 28, by a riser 30. The subsea test tree 26 is disposed above a well 32 which may comprise at least one wellbore 34. In the example illustrated, a cutting and sealing system 36 is mounted in the subsea test tree 26 and comprises a valve 38, such as a ball valve having a ball element 40 which is pivotable and may be actuated to an open position allowing access through a subsea test tree passageway 42 or to a closed position blocking access through passageway 42. The ball element may be pivotably mounted to a supporting housing 44 which surrounds the ball element 40 and may be part of the subsea test tree 26. In some applications, the housing 44 and the cutting and sealing system 36 may be designed as a modular system for selective connection into the subsea test tree 26 or into other suitable equipment.

The cutting and sealing system 36 also comprises a cutter 46 which may be mounted in the supporting housing 44. In this type of embodiment, the housing 44 serves as a common housing for both the ball valve 38 and the cutter 46. For example, the housing 44 may be a unitary structure which supports both the valve 38 and the cutter 46 at separate locations but in close proximity to each other along the overall subsea test tree passageway 42.

Depending on the subsea application, a conveyance 48 may be used to convey tools and/or other equipment down through riser 30 and subsea test tree 26. The passageway 42 is sized to accommodate passage of the tools, equipment and conveyance 48 down into wellbore 34. Upon the occurrence of certain events, the passageway 42 may be rapidly closed to shut in the well 32 by actuating cutter 46 to sever the conveyance 48 while also actuating valve 38 to shift ball element 40 to a closed, sealed position. The ball element 40 is designed to automatically form a gas tight seal upon pivoting to a closed position. Depending on the design of valve 36 and on the environment in which it is employed, a variety of actuators 50 may be used to actuate ball element 40 between open and closed positions. By way of example, actuators 50 may comprise hydraulic actuators, e.g. rod pistons, other hydraulic actuators, electrical actuators, e.g. solenoids, electromechanical actuators, or other suitable actuators designed to rotate the ball 40 between open and closed positions.

Referring generally to FIG. 2, an embodiment of cutting and sealing system 36 is illustrated. In this embodiment, cutter 46 comprises a shear ram type cutter and valve 38 comprises a strip through ball valve. The cutter 46 and ball valve 38 are packaged together in housing 44 which, in this example, is a unitary housing structure 52. For example, unitary housing structure 52 may comprise a single piece housing structure into which both ball valve 38 and cutter 46 are mounted. The housing 52 may be a modular type housing selectively mounted in subsea test tree 26, or the housing 52 may be part of subsea test tree 26.

In the illustrated example, cutter 46 is designed with capabilities for cutting several types of subsea intervention media, e.g. coiled tubing, wireline, slickline, braided line, or other types of conveyances. The cutter 46 comprises at least one actuator 54 coupled with a cutter blade 56 and oriented for selective movement into passageway 42 when conveyance 48 is to be severed. In the specific embodiment illustrated, cutter 46 comprises a plurality of actuators 54, e.g. two actuators, coupled with a plurality of corresponding cutter blades 56. The actuators 54 are mounted in housing 52 and oriented in a radial direction such that the cutter blades 56 move radially into and out of passageway 42.

Depending on the application, a variety of actuators 54 may be employed, including hydraulic actuators, electromechanical actuators, and other suitable actuators. In the example illustrated, the actuators 54 are hydraulic actuators and each actuator 54 utilizes a piston 58 slidably mounted in a corresponding cylinder 60. The pistons 58 may be actuated or moved along corresponding cylinders 60 by hydraulic fluid introduced through and/or discharged through appropriate hydraulic ports 62. The cylinders 60 and pistons 58 may be mounted in housing 52 by an appropriate coupling structure 64 and oriented in a radial direction, as illustrated.

In the embodiment illustrated, valve 38 is a ball valve having ball 40 pivotably mounted within housing 52 and biased into sealing engagement with a seal 66. By way of example, the seal 66 may be mounted in a floating seal retainer 68 captured in a corresponding recess 70 formed within housing 52. The ball 40 may be biased against seal 66 by an appropriate spring biased structure. For example, an actuating ring 72 may be engaged with ball 40 and biased by a spring 74 positioned between the actuating ring 72 and a support structure 76 located within or forming part of housing 52. As described in greater detail below, the actuating ring 72 may be designed to induce pivoting motion of ball 40 as ball 40 is transitioned between open and closed positions.

Ball valve 30 and ball element 40 may have a variety of configurations designed to selectively enable or block flow of fluid along the overall through passageway 42. For example, ball 40 comprises an internal ball passage 78 sized to accommodate fluid flow and to allow movement of conveyance 48 therethrough. The ball 40 also may comprise a relief area 80 positioned to allow the ball 40 to start closing before the conveyance 48 is pulled clear of the ball passage 78. Additionally, ball element 40 may comprise a rounded edge or edges 82, e.g. rounded lead edges, to further promote strip through capability with respect to severing and removing conveyance 48. For example, the lead edge 82 along the circumference of ball passage 78 closest to cutter 46 may be rounded to facilitate strip through.

In the example illustrated, the ball valve 38 and cutter 46 are positioned in close proximity to each other within housing 52. For example, ball valve 38 may be assembled in housing 52 in a manner so the distance between the seal location and the shear location is minimized. The seal location is created by seal 66 acting against an exterior surface 84 of ball 40, and the shear location is the location at which cutter blades 56 move to engage conveyance 48 when cutting through and shearing the conveyance. In FIG. 2, the distance between the seal location and the shear location is labeled by reference numeral 85 and in many applications is less than 10 inches (25.4 cm). However, some applications are designed to utilize very rapid sealing off of the passageway 42 upon severing of the conveyance 48, and the distance is less than 5 inches (12.7 cm). Some embodiments utilize a distance 85 of less than 4 inches (10.2 cm) which, along with the use of relief area 80, enables extremely rapid sealing following cutting of the conveyance 48 even though cutter 46 and ball valve 38 are separated and operated at unique locations along passageway 42. This type of packaging provides a very short distance between the shear and seal planes and allows the sheared medium, e.g. conveyance 48, to be cleared from the ball passage 78 very quickly when the ball valve 38 closes.

In a shearing and sealing operation, hydraulic fluid is delivered to actuators 54 and into cylinders 60 via the appropriate ports 62. The pressure of the hydraulic fluid drives the pistons 58 in a radially inward direction, as illustrated in FIG. 3. The radially inward movement of pistons 58 drives cutter blades 56 into and through conveyance 48, e.g. coil tubing, wireline, or slickline, until the conveyance is severed at the shear location.

Once the conveyance 48 is sheared, the portion of conveyance 48 on the ball valve side of actuators 54 may be withdrawn and pulled out of ball 40 along ball passage 78. The ball 40 is then pivoted to a closed position which blocks flow of fluid along passageway 42, as illustrated in FIG. 4. Use of relief area 80 allows initiation of the pivoting of ball 40 to the closed position prior to full removal of the conveyance 48 from ball passage 78. Even if the conveyance 48 does not fully clear the ball valve 38, the optimized, e.g. low, closing force exerted by actuator 50 prevents pinching of the conveyance 48 and facilitates strip through of the conveyance. Other characteristics which facilitate strip through capability of the ball valve 38 comprise the use of relief area 80 and/or the use of rounded edges 82, such as the rounded lead edge. The low biasing force, the relief area, and the rounded edges cooperate to lower the risk of pinching and facilitate the strip through capability of the valve.

Ball 40 may be pivoted between open and closed positions by a variety of mechanisms, however the illustrated example utilizes a ball operator in the form of actuating ring 72. As actuating ring 72 is shifted from a first position, as illustrated in FIG. 3, to a second position, as illustrated in FIG. 4, the actuating ring 72 causes pivoting motion of ball 40 between positions, e.g. between open and closed positions. In the example illustrated, actuating ring 72 comprises engagement features 86 which are coupled with corresponding engagement features 88 on ball 40, as illustrated in FIG. 5. For example, engagement features 86 may comprise nubs or other extensions and corresponding engagement features 88 may comprise slots designed to receive engagement features 86.

As the actuating ring 72 is transitioned linearly between positions, the engagement features 86 are moved along corresponding engagement features 88 in such a manner that ball 40 is forced to selectively pivot between open and closed positions. Movement of actuating ring 72 (or other ball operator) may be selectively caused by suitable ball actuators 50. In a specific example, ball actuators 50 comprise rod pistons 90 which may be selectively operated to move actuating ring 72 between positions. The rod pistons 90 may be hydraulically actuated and are designed to provide sufficient force to rotate ball 40 without having too high of a force that could otherwise cause the sheared medium 48, e.g. conveyance, to be pinched. This facilitates stripping of the medium 48 through the ball valve 38. It should be noted that ball 40 may be designed with generous radii on the ball valve edges, e.g. lead edge 82, to facilitate the strip through process and the closing off of passageway 42.

Referring generally to FIG. 6, another embodiment of cutting and sealing system 36 is illustrated. In this embodiment, many of the features are similar to features illustrated and described in FIGS. 2-5 and those features have been labeled with common reference numerals. However, the embodiment illustrated in FIG. 6 employs a different method of sealing the ball valve 38. In this example, the ball 40 floats and is captured between a plurality of seals 92 in which at least one seal 92 is located on each opposing side of ball 40. For example, at least one seal 92 may be positioned between housing 52 and ball 40 on the side of ball 40 closest to cutter 46 and at least one seal 92 may be positioned on an opposite side of the ball 40 between support structure 76 and ball 40.

When the ball valve 30 is transitioned to a closed position, as illustrated in FIG. 6, the ball 40 is sealed against the seal or seals 92 on one side of the ball depending on the direction of pressure acting against the ball 40. In this example, the ball valve 38 similarly functions as a strip through ball valve and may utilize rounded edges 82. In the embodiment illustrated, however, the ball 40 is constructed without relief area 80 to facilitate sealing on either side of the ball 40. Thus, the medium/conveyance 48 is stripped through the entire ball 40 and ball passage 78 prior to shifting the ball 40 to the closed position.

The cutting and sealing system 36 may have a variety of configurations for use in subsea applications and other applications. Additionally, the components and materials used in constructing the valve 38 and/or cutter 46 may vary from one application to another depending on operational and environmental parameters. The cutting and sealing functions may be performed by a variety of individual or plural cutting blades and seals, respectively. Similarly, the valve actuation mechanisms may rely on hydraulic systems powered via control lines, wellbore pressures, pressure storage devices, or other suitable pressure sources. The valve actuation mechanisms and cutter actuation mechanisms also may utilize electrical actuators, electromechanical actuators, combinations of actuators, and other suitable mechanisms for achieving the desired actuation. Cutter blades and cutting edges also may be designed from a variety of components and/or materials which may be selected based on the environment and/or materials to be cut.

Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims. 

What is claimed is:
 1. A system for use in a subsea test tree, comprising: a subsea test tree housing having a passageway sized to receive a conveyance therethrough; a cutter mounted along the passageway, the cutter comprising a plurality of cutter blades selectively movable into the passageway by a plurality of pistons at a shear location; a valve mounted along the passageway separate from the cutter, the valve being a ball valve having a ball with a ball passage sized to receive the conveyance therethrough; and a seal member positioned to seal against an outer surface of the ball when the ball is pivoted to a position closing off flow along the passageway, the distance between the seal and the shear location being less than 10 inches (25.4 cm).
 2. The system as recited in claim 1, wherein the ball comprises a relief area positioned to allow the ball to start closing before the conveyance is pulled clear of the ball passage.
 3. The system as recited in claim 2, wherein the ball has a rounded leading edge at the ball passage and the ball is biased with a low biasing force against the conveyance, the low force of the bias, the relief area, and the rounded leading edge cooperating to enhance the strip through capability of the valve.
 4. The system as recited in claim 1, wherein the ball valve is actuated by rod pistons.
 5. The system as recited in claim 1, wherein the seal member is positioned in a floating seal retainer.
 6. The system as recited in claim 1, wherein the seal member comprises a plurality of seals located on opposite sides of the ball.
 7. The system as recited in claim 1, wherein the cutter and the valve are mounted in a common housing.
 8. The system as recited in claim 1, wherein the ball is biased into engagement with the seal member.
 9. The system as recited in claim 1, wherein the distance between the seal and the shear location is less than 5 inches (12.7 cm).
 10. The system as recited in claim 1, wherein the distance between the seal and the shear location is less than 4 inches (10.2 cm).
 11. A method of shutting in a well, comprising: positioning a valve along a flow path through a subsea test tree; providing the valve with a ball pivotable between open and closed positions with respect to the flow path; locating a cutter along the flow path to create a shear location for cutting of a conveyance positioned in the flow path and through the ball; and arranging a seal member to seal off the flow path by sealingly engaging the ball at a location less than 10 inches (25.4 cm) from the shear location.
 12. The method as recited in claim 11, wherein arranging comprises arranging the seal member to engage the ball at a location less than 5 inches (12.7 cm) from the shear location.
 13. The method as recited in claim 11, wherein arranging comprises arranging the seal member to engage the ball at a location less than 4 inches (10.2 cm) from the shear location.
 14. The method as recited in claim 11, further comprising cutting a coiled tubing conveyance with the cutter and then pivoting the ball prior to withdrawal of the coiled tubing from an internal passage of the ball.
 15. The method as recited in claim 11, further comprising cutting a wireline conveyance with the cutter and then pivoting the ball prior to withdrawal of the coiled tubing from an internal passage of the ball.
 16. The method as recited in claim 11, wherein locating the cutter comprises providing piston mounted cutter blades oriented for selective movement into the flow path.
 17. The method as recited in claim 11, wherein arranging the seal member comprises utilizing seals on opposite sides of the ball.
 18. A system, comprising: a valve comprising: a ball valve element rotatably mounted in a housing, the ball valve element having an exterior surface and a passageway sized to receive a conveyance therethrough; a cutter located in the housing at a position spaced from the ball valve element and oriented for selective severing of the conveyance; and a seal system positioned to act against a surface of the ball valve element.
 19. The system as recited in claim 18, wherein the cutter comprises at least one blade mounted on at least one piston.
 20. The system as recited in claim 18, wherein the ball valve element is actuated by rod pistons. 